Making a telescope using a rubber ball

drmorbius (Randall) · #1 06-07-2006, 01:52 PM

And now for something completely different... this bloke has made a telescope with an interesting mount for an ATM project. Not sure if it has any advantages over Eq or Dob mounts, but I'd give him an A+ for clever and being different.

He calls it the Trackball Telescope...

http://www.sff.net/people/J.Oltion/trackball.htm

ving (David) · #2 06-07-2006, 02:04 PM

look practical enough. you gunna make one Doc?

sheeny (Al) · #3 06-07-2006, 04:30 PM

de ja vu!

there's another thread here in exactly the same link, posted same day... doo, doo ,doo, doo... doo, doo, doo, doo...

very innovative and elegant idea! I like it! I'd like to know how well it performs in practice...

Looks to me like the ball rests on three supports: 1 acts as a pivot point (or axle) and the other two drive the ball so it can track. So it looks to me like it has a lot of the simplicity of a push-to dobbie, the ability to track and you should be able to rotate the tube for convenience (of looking into the EP!)

Could be a challenge to mount a camera on? (and keep it balanced that is!)

Thanks for posting!

Al.

circumpolar (Matt) · #4 06-07-2006, 08:01 PM

Quote:

Originally Posted by sheeny

Could be a challenge to mount a camera on? (and keep it balanced that is!).

You could build one of these especially for your camera only!

or

make it the base for a solar projection system and use a refracting lens like a finderscope or small binoculars, projection card and extendable arm to hold the lens.
Could be a good way to track sunspots and transits.
Make it small enough and you would use it all the time at a seconds notice.

Gargoyle_Steve (Steve) · #5 08-07-2006, 03:00 AM

I love the simplicity and efficiency of his design. It just seems to fit right in with the whole "elegant universe" thing - mathematically clean and simple - fantastic.

Damn I'd love to build one of those!

Starkler (Geoff) · #6 08-07-2006, 09:40 AM

An interesting design but not very flexible with regards to being limited with what you can put in the focuser without upsetting the fine balance required.

Gargoyle_Steve (Steve) · #7 09-07-2006, 12:48 AM

The more mass that is in the base, the less the weight at the focuser will matter. Design it so that you can add/remove additional "balance" weights if needed, or make the sphere itself heavier to maintain even weight distribution at that end. Metal sphere for instance??

Starkler (Geoff) · #8 09-07-2006, 12:27 PM

Quote:

Originally Posted by Gargoyle_Steve

The more mass that is in the base, the less the weight at the focuser will matter. Design it so that you can add/remove additional "balance" weights if needed, or make the sphere itself heavier to maintain even weight distribution at that end. Metal sphere for instance??

I think on the constructors site it mentioned that the centre of gravity of the ota should be at the centre of the sphere. This means that at the focuser end you have a lever of comparitively very long length working against a much shorter one of half the radius of the sphere. A small change of weight at the focuser requires a change many times that in the bottom of the sphere.

The simplest solution maybe is to weight the sphere to balance for the heaviest forseeable load at the ep end, and use removable weights there (at the ep end) to balance for anything lighter.

This is the way I went with my dob. Im balanced for my 31mm nagler, and I move a speaker magnet up the tube to compensate for lighter eyepieces.

rmcpb (Rob) · #9 10-07-2006, 01:09 PM

That design is just brilliant!! Wonder how it would go in a longer focal length? Probably need a heap of lead shot in the bottom but its simplicity is so elegant.

Project # 145236 now doing project # 129

Have to be patient

netwolf · #10 10-07-2006, 02:02 PM

The best thing about it is that it is easy to demonstrate the need and theroy of polar alignment to kids/adults.

As can bee seen in this image. They clearly show how the stars move around the celstial pole and help explain the need for polar aliginment
http://www.sff.net/people/J.Oltion/B...at%20lines.jpg

netwolf · #11 10-07-2006, 02:08 PM

and what abou the other designs page. Check out the article about the Edmund astroscan and simple way to make it robotic.. Wow. I got get me one of those...

http://www.sff.net/people/J.Oltion/T...m#otherdesigns

netwolf · #12 10-07-2006, 02:36 PM

Some more usefull information on the concept behind the sphere design.
http://home.earthlink.net/~celstark/id12.html